The invention relates to a method of and an arrangement for rolling down of hot-rolled wide strips from continuously cast thin slabs in successive operational steps in a pitch line, wherein a separate thin slab is cut off from a continuously cast strand produced in one of several casting lines, is homogenized and is brought up to a predetermined temperature in an equalizing furnace, is transported to a movable furnace portion formed as a regenerative portion, a buffer portion or an equalizer portion, as the case may be, and is then transported to a regenerative furnace arranged in the pitch line, from which the separate thin slab is transported to an additional holding furnace, if needed, and therefrom to the rolling train.
If the thin slab after casting is not reeled, it requires a rather long furnace installation. For example, a standard furnace installation for two or three casting lines provides for transporting of thin slabs longitudinally or transversely to a rolling train. Such a installation is described, for example, in European patent EPIO438,066. The arrangement described in this patent includes, for rolling down a hot-rolled wide strips from a thin slab in a continuous finishing train, three casting lines, wherein the middle casting line is arranged along the same line as the finishing train. The transportation of the thin slab from a casting line to the finishing train is effected by two "ferries", which operate as combined longitudinal/transverse/longitudinal transportation system, in which the "ferries" are selectively aligned sidewise with adjacent casting lines. Such a layout of the arrangement permits to achieve a substantial reduction of the cycle time of loading of thin slabs into the finishing train for producing hot-rolled thin strips, if the following conditions are maintained:
(a) the time of loading of a thin slab, which is separated from a cast strand, into longitudinal/transverse/ longitudinal transportation system corresponds to the time of unloading of a thin slab from the transportation system, and PA1 (b) the rolling-down time of a thin slab is greater than the transportation time of the longitudinal/transverse/ longitudinal transportation system plus loading or unloading time.
With this arrangement, it is important that each casting line cooperates with a furnace, an equalizing region and a buffer region, provided in front of the transportation system, and that downstream of the transportation system and before the finishing train, a holding furnace is provided.
With the known arrangement concept, the drawback of having a significantly long furnace installation is compensated by the reduction of the cycle time of loading of the finishing train. The length of the furnace installation is about 210 m, and providing such a furnace installation necessitates high investment expenditure for both the furnace installation and the shop construction.
In order to reduce the investment expenditure and the required area as well as to improve the temperature regime, EPO 413169 proposes another arrangement concept for producing steel strips with the use of one or several steel strip casting machines, together with associated temperature equalizing furnaces. According to this concept, the finishing train is arranged opposite the output conveyor of the steel strip casting installation and is offset relative to the conveyor, and an additional transportation temperature equalizing furnace is arranged sidewise of a transportation temperature equalizing furnace, which is arranged adjacent to the outlet of the steel strip casting installation. The additional temperature equalizing furnace is offset relative to the first temperature equalizing furnace in a direction of the strip displacement. The two temperature equalizing furnaces are connected by an end face crossover transportation device. This concept permits reduction of the length of the furnace installation almost by half. However, the drawback of this concept consists in that the furnace dwell time of the slab front and rear portions depends on the difference between the casting and feeding speeds and is increased due to the change of the movement direction. A further drawback is that the furnace installation must be closely associated with the casting installation.
An object of the present invention is to provide a method of rolling down of hot rolled wide strips from continuously cast thin slabs in successive operational steps in a pitch line, wherein a separate thin slab is cut off from a cast strand produced in one of several casting lines, is homogenized and is brought up to a predetermined temperature in an equalizing furnace, is transported to a movable furnace portion formed as a regenerative furnace portion, a buffer portion, or an equalizer portion, as the case may be, and is then transported to a regenerative furnace arranged in the pitch line, from which the separate thin slab is transported to an additional holding furnace, if needed, and therefrom to a rolling train.
Another object of the invention is a suitable arrangement for effecting the method and which would permit to reduce the length of the furnace installation in comparison with the rolling down arrangement in which the slab is transported straight forward, without any operational technical drawbacks or the need in a more complicated equipment.